The objectives of this contract are: 1) to maintain a colony of approximately 60 strains of inbred mice by strict pedigreed brother-sister matings; 2) to breed and develop new congenic mouse strains; 3) to make selective crosses and backcrosses between these strains; 4) to produce antisera and hybridomas by immunization between these strains and appropriate fusions; and 5) to perform quality control testing by serology skin grafting and DNA analysis of pedigreed animals in the colony.